The metathesis, or in other words the disproportionation, of olefines relates to a reaction wherein one or more olefines are converted into olefines having a different molecular weight. An olefine may be disproportionated with itself into an olefine having a higher molecular weight and into an olefine having a lower molecular weight. In this case, the reaction may be called "self-disproportionation". Two different olefines may also be converted into other olefines by means of the metathesis reaction
In order to function, the metathesis reactions of olefines require a catalyst system, which includes a transition metal compound, often a cocatalyst and sometimes also a compound acting as a promoter. The catalyst systems based on tungsten or molybdenum are especially efficient. Such catalysts generally comprise a tungsten or molybdenum oxide on an inorganic carrier, which is e.g. silica or alumina. It is known to add different substances as a promoter to such catalyst. Thus, e.g. according to EP publication 152,112, tungsten oxide or other titanium-containing substances are added to the surface of the catalyst as a promoter According to U.S. Pat. No. 4,559,320, it is known to use a tungsten catalyst on a silica carrier, into which magnesium oxide is additionally mixed. According to EP publication 56,013, a catalyst composition is known comprising a molybdenum oxide or a tungsten oxide on a silica carrier.
According to U.S. Pat. No. 3,956,178, a metathesis catalyst of three components is known, which catalyst is prepared from a tungsten compound, an organic ligand and an organo-metallic compound. In this patent, the tungsten compound is a titanium oxychloride and the organic ligand contains a nitrile or ester group. As examples of ligands are mentioned phthalodinitrile, adipo nitrile and ethyl phthalate.
According to U.S. Pat. No. 4,550,216, a metathesis catalyst is known, which comprises a compound of tungsten, a halogen and a phenoxy group, which compound is possibly substituted.